In this project we hope to establish a stable xenogenic (macaque-human) lymphopoietic chimeric M. nemestrina. We hypothesize that these macaque-human chimerics will enhance the infectivity of HIV-1 in these species, and that the chimeric system will be capable of sustaining replication of the virus in vivo. This procedure is planned as follows fetal macaques, about 30-40 days gestation, will be inoculated with hematopoietic stem cells recovered from human umbilical cord blood or fetal liver tissue. One fetus inoculated with this procedure was born with a high level of engraftment and chimerism. Further work in this direction is warranted.